In my last opinion editorial I talked about the evolution of a new player slowly bringing themselves into the world of Shadowrun. So now we'll fast forward a bit, they know the roles and they have an idea that is just awesome.
GM: So what are you playing?
Noob: I want to make a Mystic Adept/Face/Rigger.
GM: Mother of god..
On the surface a jack-of-all-trades seems like a good idea. In a pinch, you can fill in for someone not there. Mage player got a case of the flu? Game on, I can sling spells! Face player out on a date? Well, I have social skills and two contacts, LET'S DO THIS!!
There are a few points where this can be problematic. Some "multi-classing" can be good, there are natural synergies that work well. Physical Adept/Face. Your magic enhances your skills as well as your physique. Decker/Drone Rigger. You handle tech, and you're good at it. Street Sam/Covert Ops. You are a high-tech ninja.
Where this breaks down is when you get into triple dipping. When you get into three roles your dice begin to dilute to the point of you start to go from Jack-Of-All-Trades to Master-Of-None.
Sure in a pinch your Mystic Adept role can fill in for a caster and a street sam. However in that aspect you've spent skills towards two roles. Casting and fighting. You're also a Face on the side. So those two roles get spread a little thinner because you need 3 to 6 social skills to be an effective Face.
Next you throw in being a wheelman, your Priorities have to shift because had to have Resources high to get all your vehicles and drones. So now your Mystic Adept/Face aspects suffer from having lower attributes and skills split between four roles (Magic/Fighting/Social/Tech).
Say your team is okay with that. Sure your character might not be as effective at things as the "single class" characters, but you're a solid player and they like gaming with you.
Enter the new player.
Your group has a street sam, a tech-ninja, a decker and your Mystic Adept/Face/Rigger.
GM: What would you like to play? New player: I was thinking I would like to play a B&E type. GM: Well that's great we have a tech-ninja the two of you could work together! New Player: Oh you have a B&E type already? I suppose I could play a decker. GM: Oh we have a technomancer. New Player: Face? GM: Dave. New Player: Mage? GM: Dave. New Player: Rigger? GM: Dave again.. New Player: Street Sam? GM: Sam, Tech-Ninja and Dave...
By taking up more than two roles you weaken your character and you make it harder for new people that might join the campaign to have an area to shine in. Either they're not playing what they would really enjoy, they're second-stringing someone, or they're outshining the generalist making an established player have less of an impact on the game.
Nothing sucks worse than being left sitting in the van on a run because you're not needed.
So in closing, pick one or two things your character is good at. Be GOOD at those, and trust your fellow players to do the same. Shadowrun is about running as a team, you will always have others to count on you don't need to be an Army of One.